The Biosphere Total mass of organic carbon in the biosphere : 5E18 g C 20% in living organisms 80%...
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The Biosphere Total mass of organic carbon in the biosphere : 5E18 g C 20% in living organisms 80% compounds arising from the decay of living organisms (e.g. humus) Sum total of all living and dead organisms in the Earth system
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Transcript of The Biosphere Total mass of organic carbon in the biosphere : 5E18 g C 20% in living organisms 80%...
The Biosphere
Total mass of organic carbon in the biosphere : 5E18 g C20% in living organisms80% compounds arising from the decay of living organisms (e.g. humus)
Sum total of all living and dead organisms in the Earth system
Composition of the biosphere
Importance of C,H,O
Simplification : A generic chemical formula to represent the composition of the bisophere as the stoichiometric equivalent of glucose . Glucose is the ‘building block’ from which other molecules are synthesized in the biosphere.
“CH2O”Glucose: C6H12O6
Other important elements (nutriments) : N, P trace elements (oligo-elements)
Biospheric molecule
Metabolic processes
Autotrophism (photo,chemo) : Synthesis of living protoplasm from minerals (require energy)
Heterotrophism (chemo): Synthesis of living protoplasms from organic molecules
Biosynthesis (or anabolism) : construction of living protoplasm (living content of a cell)
Catabolism: breaking down of organic polymers as a source of energy
2Photosynthesis
Respiration or decay of organic matter
Oceanic biosphere
The Redfield ratio : represents the average ratio between C,N,P in the ocean biota. It is currently estimated to be 106:16:1
N and P are essential nutrient that have to be introduced in the simple photosynthesis / respiration –decay reactions
photosynthesis
respiration
is replacing “CH2O”
However part of H20 generated is released in the environment and lower the content of O and H in the organic polymers. To account for that it is assumed that biomass is synthetised by combining CO2 and H2O is ratio greater than 1:1, e.g 106:64 . Finally a more representative equation could be:
Continental biosphere
The mass of continental biosphere is dominated by tree, rich in lignine and have lower O:C, H:C, and N:C ratios than marine biomass. The budget between photosynthesis and respiration could be written as :
Continental “biospheric molecule”
Primary production
Rate at which C is assimilated or fixed by green plants.Fundamental parameters in Biogeochemical cycles.
Gross primary production rates (GPP): Total C assimilated by green plantsNet primary production (NPP): Account for respiration loss For terrestrial biosphere, about 50% of the GPP is estimated to stay in the biosphere as NPP (global scale estimation).
LF: litter fall
D: decay
GSOP: gross surface oceanic prod.
NSOP: Net surface oceanic prod.
U: Upwelling
S: Sedimentation
Rp: respiration in the photic zone
NPP = GPP - Rgp
